This is a breakout board for the very useful 16-Channel Analog/Digital Multiplexer/Demultiplexer CD74HC4067. This chip functions like a rotary switch, internally connecting the common pin (COM on the schematic, SIG on the device) to one of the 16 channel pins (CHANxx). It works with digital and analog signals (the voltage cannot be higher than VCC), and the connections operate in a bidirectional manner.

To control it, connect 4 digital outputs to the chip's address select pins (S0-S3) and send it the binary address of the desired channel (see the datasheet for details). This allows you to connect up to 16 sensors to your system using only 5 pins!

Since the mux/demux also works with digital signals, you can use it to route TTL level data to or from many devices. For example, you could use it to connect the TX pins from 16 devices to one RX pin on your microcontroller. You can then select any of those 16 devices to listen to.

If you want bidirectional communications, you can add a second board to route your microcontroller's TX line to 16 devices' RX lines. Using multiple boards, you can create similar arrangements for I2C, SPI, etc.

The internal switches are bidirectional, support voltages between ground and VCC, have low "on" resistance and low "off" leakage, and to prevent cross-talk, they perform "break-before-make" switching. The board also brings out the chip's "enable" pin, which when high, completely disconnects the common pin (all switches "off").

• Operates from 2V to 6V
• "On" Resistance: 70 Ohms @ 4.5V
• 6ns break-before-make @ 4.5V
• Wide operating temperature range: -55C to 125C